The project involves studies of vertebrate neuromuscular junctions. Specifically, we will continue to examine: 1) the relationship between miniature endplate currents and acetylcholine receptor (AChR) and esterases (AChE) site densities. These studies should lead to the determination of various rate constants such as ACh binding, ACh diffusion, and AChR gate opening prevailing in the normal cleft, 2) the role of calcium in mediating necrosis in the muscle in response to prolonged ACh-AChR interaction, and 3) the control of AChR turnover in normal adult neuromuscular junctions.